ABSTRACT As San Francisco?s HIV epidemic is set to reach zero infections, Rio de Janeiro is experiencing a resurgence in new reported HIV cases among MSM. San Francisco?s success can be attributed to effective biomedical interventions, namely: rapid diagnosis, immediate ART, sustained viral load suppression, wide uptake of PrEP, and interrupting new clusters of transmission. In Brazil, however, uptake of these biomedical interventions has so far been insufficient to reverse the epidemic, despite being the first low/middle income country to provide free ART to all persons with HIV, participation in clinical trials proving PrEP efficacy, and national policy to provide free PrEP. Meanwhile, young MSM, particularly Black/Afro-Brazilians, have high HIV incidence, low viral suppression, and poor PrEP adherence. We therefore propose collaborative research between the San Francisco Department of Public Health and the Oswaldo Cruz Foundation (Fiocruz) in Rio de Janeiro. We will focus on identifying the drivers of HIV infection, ways to address barriers to biomedical interventions, and identifying the hurdles to including young MSM in biomedical research. Methods include a cross-sectional survey of MSM age 18-24 using respondent-driven sampling adapted for social media-based sampling; development of a technology-based rapid ART and PrEP engagement and retention intervention; and a qualitative study of MSM age 15-17, their parents, and providers of sexual health services to better understand the onset of risk and the feasibility of increasing inclusion of minors in biomedical HIV research and intervention programs. San Francisco stands as an American test case for the elimination of HIV, yet remaining challenges exist in reaching young and minority MSM. Rio de Janeiro is an engine of HIV research in South America, yet faces challenges in reaping the benefit of proven biomedical interventions for MSM. The proposed US-Brazil research collaboration will provide mutual benefit in increasing the effectiveness of biomedical interventions to reverse the HIV epidemic among MSM in Brazil and address remaining disparities in the US.